Alexander J. Felson

Challenges and future directions in urban afforestation

Summary 1. Mature urban trees improve air quality, reduce storm water run-off and sequester carbon. Municipal agencies establish forests of native juvenile trees to enhance these and other ecosystem services to cities. Little data exist, however, regarding whether these trees will form mature, native forests. 2. We review urban forestry research that deals specifically with the growth, survival and recruitment of new native urban forests and use these data to identify knowledge gaps and propose research needed to create and maintain native urban forests. 3. Experimental urban forestry studies are few and most are of durations ≤5 years, shorter than the 10–25 year time frame required to understand forest stand dynamics. Studies capturing initial dynamics of urban afforestation (≤5 years) identify invasive species as the primary threat to native tree establishment. Data exploring longer-term dynamics are needed to evaluate whether early-stage afforestation dynamics can be used to infer the composition and function of mature urban forests. 4. Synthesis and applications. Urban afforestation approaches–from natural colonization to large-scale plantings–represent a trade-off in cost vs. efficacy for establishing native forests. A major cost-saving strategy would be to determine whether exotics and natives can co-exist and provide the intended ecosystem services.

Ecological resilience and resilient cities

The urban realm is changing rapidly and becoming increasingly interconnected across continents, and across contrasting types of land covers, while at the same time facing new environmental threats and experiencing new demographic and social pressures. The urban component of the global ecosystem can be made more sustainable by incorporating the ecological understanding of resilience into the discourse. Sustainability is seen as a social, normative goal, which can be promoted using the mechanisms of ecological resilience. Ecological resilience differs from engineering resilience. Ecological resilience emphasizes the capacity of a site to adjust to external shocks and changes in controlling interactions, while engineering resilience emphasizes its ability to return to a state that existed before perturbation. Ecological resilience is particularly appropriate to urban systems, given the extent and open-ended nature of the changes and challenges they face. Adaptive processes are explored as contributions to the achievement of a successful adaptive cycle in urban socio-ecological systems. Key tools for incorporating the ecological thinking about resilience into the social discourse include landscape or patch ecology, the novel idea of the metacity, an assessment of ecological and design models, and the use of designs as experiments.

Promoting Earth Stewardship through urban design experiments

Earth Stewardship requires a repositioning of ecological science in society to promote social–ecological change. This may place ecologists in situations that are largely unfamiliar to them, such as playing a role in the process of urban design. “Designed Experiments” – defined as projects that embed ecological research into urban design to study and shape buildings, landscapes, and the infrastructure of human settlements – are intended to enhance the impact of ecologists working in these new situations. Designed Experiments provide a framework for organizing relationships among ecologists, urban designers, decision makers, and citizens; an opportunity for testing ecological hypotheses; and a platform for experiential learning among multiple participants – all of which have the potential to aid in overcoming barriers to the goals of Earth Stewardship. Here we explore the capacity of Designed Experiments to facilitate progress toward Earth Stewardship through real-world case studies.

Involving Ecologists in Shaping Large-Scale Green Infrastructure Projects

Cities are implementing green infrastructure projects to provide ecosystem services such as storm water mitigation. The efficacy of these projects at providing services is rarely evaluated. Embedding research into project design provides a mechanism for both evaluation and development of the ecological knowledge needed to improve infrastructure for services provision. Ecologists must navigate the politics, economics, and social constraints of working in cities. Additional skills and practices are needed to develop new relationships and improve credibility, to define project roles, to identify new funding, and to integrate multidisciplinay knowledge. We examine a large-scale green infrastructure project that integrates hypothesis-driven experimental research and baseline monitoring with park design, implementation, and maintenance. Drawing on this case study, we recommend strategies to facilitate the inclusion of research ecologists in green infrastructure projects by enhancing the professional cer-tification process, establishing research ecologists as consultants, and integrating ecology and design in graduate programs.

Mapping the Design Process for Urban Ecology Researchers

The integration of research into the design process is an opportunity to build ecologically informed urban design solutions. To date, designers have traditionally relied on environmental consultants to provide the best available science; however, serious gaps in our understanding of urban ecosystems remain. To evaluate ecosystem processes and services for sustainable urban design and to further advance our understanding of social-ecological processes within the urban context, we need to integrate primary research into the urban design process. In this article, we develop a road map for such a synthesis. Supporting our proposals by case studies, we identify strategic entry points at which urban ecology researchers can integrate their work into the design process.

The Design Process as a Framework for Collaboration Between Ecologists and Designers

The expanding knowledge from urban ecological research will be critical for enhancing our ecological understanding of cities and for influencing the ability to shape cities to increase ecosystem functions and benefits. Even with the generation of data and the development of ecological theory pertinent to urban systems, the application of ecological understanding to the design and restructuring of urban systems requires additional steps. In particular, design practitioners still need to integrate and apply these ecological concepts. This chapter explores the design process as a tool for applied science. The design process is flexible enough to incorporate ecological input at different stages. However, the process itself favors the working methods of design. Through a case study, the chapter examines the interplay between designers and professional ecologists working together through the design process. This study suggests that facilitating the exchange between designers and ecologists requires a commitment on the part of the designer to provide multiple opportunities for ecological input in the process as well as a more proactive effort on the part of ecologists to provide input at those stages.

Conserving amphibians in the face of land development: integrating field experiments as a planning tool

Regulations designed to guide development practices inadequately reflect ecological understanding and fall short of preserving viable habitats. Environmental consultants use rapid assessments and monitoring on individual ponds to rank pond habitat quality, relying on coarse proxies, including vegetative indicators, soil characteristics, hydroperiod, and breeding evidence in obligate species. Planners incorporate these rankings to inform the layout of neighborhoods, roadways, infrastructure and housing. However, important drivers of amphibian survival and fecundity—including metapopulation dynamics, habitat connectivity, watershed health, terrestrial density dependence, and environmental gradients—are often poorly measured and regulated. Given that development proceeds regardless, what options exists improve land development practices? Integrating experimentation into the planning process can inform land development and improve amphibian conservation. Working as part of the design team we employed an adaptive approach called designed experiment to inform development practices. We manipulated Ambystoma opacum larvae within enclosures to test the effects of inter-pond conditions (versus intra-pond density dependence) on the survival and fecundity of conspecifics, Rana sylvatica and Ambystoma maculatum. While the A. maculatum populations were decimated with only 1.5 % survival. For A. opacum and R. sylvatica results indicate habitat variation between ponds accounted for 63.7% and 50.3% of the variance in survival rates of larvae, respectively, and are not predicted by the presence and abundance of egg masses, while density effects accounted for 3.5% and 2.8% of the variation in survival. The results suggest that ponds ranked as high value based on egg mass counts may actually function as habitat sinks. This study illustrates the potential value of assessment approaches that emphasize habitat quality across pond clusters to guide mitigation, conservation, regulations, and to establish sites and funding for ecological research.